1. Field of the Invention
The present invention relates to an external axial rotary piston blower with a housing consisting of a casing or mantle part and two side parts. The casing or mantle part encompasses inner cylindrical surfaces or raceway means formed out of two cylinders intersecting each other in a region of an inlet and outlet communicating with internal chamber means in which two identical single-wing respectively dual-wing piston means rotate, which have approach or starting surfaces with large radius along the casing raceway means and having approach or starting surfaces with small radius engaging respectively with the other piston.
2. Description of the Prior Art
Such blowers of half-roller or quarter-roller type of construction are employed and utilized preferably as superchargers, blowers or compressors for internal combustion engines. The compression or compacting of the operating medium arising hereby is adequate to bring about a heat expansion of the housing on the pressure side thereof, while the suction side of the housing is cooled by the nearly uninterrupted flow of cold operating medium coming thereto and consequently not experiencing or suffering any heat distortions or warpage. The same is true for pistons of which approach or starting surfaces with large radius constantly come into engagement with cold operating medium. Thereby an expanding of the housing results in operation on a pressure side of the housing both in radial direction as well as an axial direction, while the piston means in a very much more nominal extent or measure are subject to such heat expansions. For this reason, just upon the pressure side particularly there result gaps that are too wide between the casing raceway surfacing and approach or starting surfaces of the piston with large radius on the one hand and between the side walls of the piston and the side walls of the housing upon the pressure sides thereof on the other hand. Since the housing preferably consists of aluminum, these heat expansions have greater meaning attributable thereto. The heat expansions at higher speeds and pressures lead to supply or delivery losses and capacity or efficiency losses, which under all circumstances should be avoided.